As antioxidants, preservatives and starting materials for other chemicals, there are generally known alkoxyalkyl group substituted phenols such as, for example, 2,6-di-t-butyl-4-methoxymethylphenol.
Hitherto, there have been many processes for producing the alkoxyalkyl group substituted phenols.
For example, a process is known which comprises reacting a phenol such as 2,6-di-t-butylphenol, an alcohol and formaldehyde in the presence of a tertiary amine derived from phenols such as, for example, N,N-dimethyl-3,5-di-t-butyl-4-hydroxybenzylamine (Mannich base).
However, yield obtained by this process is about 82% and is not satisfactory. Besides, since the objective product and the catalyst are similar in their structure, separation from each other is not easy.
It is also known to react a phenol such as 2,6-di-t-butylphenol, an alcohol and formaldehyde in the presence of a hydroxide of alkali metal to produce an alkoxyalkyl group substituted phenol.
However, yield of alkoxyalkyl group substituted phenol in this process is low of less than about 50%.
U.S. Pat. No. 2,838,571 discloses a process for production of alkoxyalkyl group substituted phenols by reacting a 2,6-dialkylphenol, formaldehyde and an alcohol in the presence of a metallic hydroxide.
However, yield of alkoxyalkyl group substituted phenols according to this process is also unsatisfactory.
On the other hand, U.S. Pat. No. 4,633,022 filed on Sept. 16, 1985 in U.S.A. and issued on Oct. 30, 1986 discloses a process for producing a bisether represented by the formula (A): ##STR3## which is different from the objective alkoxyalkyl group substituted phenols of this invention by reaction of a 2,6-dialkyl substituted phenol with formaldehyde in methyl alcohol in the presence of a tertiary amine.
According to the process disclosed in the above U.S. Pat. No. 4,633,022, the bisether represented by the above formula can be obtained by reacting a 2,6-dialkyl substituted phenol with formaldehyde in methanol in the presence of a tertiary amine under inert gas atmosphere.
However, tracing experiments by the present inventors repeating examples given in U.S. Pat. No. 4,633,022 has revealed that the bisether claimed in U.S. Pat. No. 4,633,022 cannot be produced by the process disclosed in U.S. Pat. No. 4,633,022.
That is, in utterly the same manner as in Example 1 of U.S. Pat. No. 4,633,022, 206 g (1 mol) of 2,6-di-t-butylphenol, 500 ml of methanol, 36 g (1 mol) of paraformaldehyde and 125 ml (0.9 mol) of triethylamine were refluxed under nitrogen stream of 1 atm at 70.degree. C. over a period of 16 hours.
The reaction mixture was subjected to atmospheric distillation to remove 250 ml of a mixture of methanol and triethylamine and the residue was cooled to 25.degree. C.
Crystal separated by this cooling was filtered, washed with 50 ml of methanol five times and then dried.
Yield of the resulting crystal was 157.5 g (Yield is 233 g according to the disclosure of U.S. Pat. No. 4,633,022).
The crude crystal separated after the atmospheric distillation was analyzed by gas chromatography to obtain the GC analysis chart as shown in FIG. 1. Conditions of the gas chromatography are shown below.
GC analytical device: SHIMAZU GC-9A (Shimazu Seisakusho, Ltd.)
FID PA1 Column: 2 m PA1 Packing material: Dexsil 300GC Uniport HP PA1 Injection temperature: 250.degree. C. PA1 Column temperature: 70.degree.-250.degree. C. PA1 Heating rate of column: 10.degree. C./1 min for 70.degree.-150.degree. C.; 25.degree. C./1 min for 150.degree.-250.degree. C. PA1 Carrier gas: Nitrogen PA1 Conditions of GC are same as above PA1 Conditions of MS: HITACHI M80B type double focusing mass spectrometer (Hitachi Limited) PA1 Ionization voltage: 70 eV PA1 Accelerating voltage: 3 KV PA1 Ion source temperature: 200.degree. C. PA1 Scanning speed: 1-500 n/z (sec)
As shown in FIG. 1, 8 peaks were found in the GC analysis chart as a result of gas chromatography analysis.
Substances given said 8 peaks were analyzed in GC-MS analysis to be identified as the compounds represented in Table 1. The yield of these compounds were represented in Table 1. analysis are as follows.
GC-MS analytical device
TABLE 1 ______________________________________ Peak Yield NO. Products (mol %) ______________________________________ (1) Methanol (2) Triethylamine (3) 2,6-di-t-butylphenol (4) 2,6-di-t-butyl-p-cresol 2.5 (5) 2,6-di-t-butyl-4-methoxymethylphenol 74.5 (6) 2,6-di-t-butyl-4-hydroxymethylphenol 2.1 (7) 2,6-di-t-butyl-4-hydroxymethoxymethylphenol 1.8 (8) 4,4'-Methylene-bis-(2,6-di-t-butylphenol) 2.5 ______________________________________
In this case, conversion rate of all products was 79.8% based on 2,6-di-t-butylphenol.
The present inventors have doubted if there are errors in the results of their tracing experiments of Example 1 of U.S. Pat. No. 4,633,022 and they carried out hydrogenation decomposition of the principal product (product shown by peak (5)) obtained by the above GC analysis in the presence of a catalyst. If the product shown by the peak (5) is the bisether disclosed in Example 1 of U.S. Pat. No. 4,633,022, trisubstituted phenol and water should be produced as shown in the following reaction formula (B). ##STR4##
However, according to the experiments conducted by the present inventors, BHT and methyl acetate were produced, although acetic acid was used as a solvent. From the results, it is reasonable to consider that in Example 1 of U.S. Pat. No. 4,633,022, bisether as shown by the formula (A) was not produced, but 2,6-di-t-butyl-4-methoxymethylphenol was produced. Moreover, .sup.1 H-NMR analysis of the product indicated by the peak (5) showed that said product was 2,6-di-t-butyl-4-methoxymethylphenol as shown in FIG. 2. Results of elemental analysis of the product shown by the peak (5) are as follows.
______________________________________ Elements Found Calculated ______________________________________ C 76.52 76.75 H 10.66 10.47 ______________________________________
Thus, it was supported that the product was 2,6-di-t-butyl-4-methoxymethylphenol.
Therefore, it has been clarified by the present inventors that according to the process disclosed in U.S. Pat. No. 4,633,022, not bisether, but 2,6-di-t-butyl-4-methoxymethylphenol is produced as a principal product.
Moreover, according to Example 3 shown as a comparative example in U.S. Pat. No. 4,633,022, use of sodium hydroxide in place of triethylamine as catalyst in Example 1 resulted in reduction of yield to 58%. However, U.S. Pat. No. 2,838,571 and J. Am. Chem. Soc., 5019 (1957) disclose that when 2,6-di-t-butylphenol, methanol and paraformaldehyde are reacted using sodium hydroxide as a catalyst, 2,6-di-t-butyl-4-methoxymethylphenol is produced.
As mentioned above, the invention described in U.S. Pat. No. 4,633,022 does not disclose technical facts. Therefore, the invention described in U.S. Pat. No. 4,633,022 cannot be prior art.
Even if U.S. Pat. No. 4,633,022 can be prior art, this U.S. Pat. No. 4,633,022 discloses bisetherification reaction of two molecules of 2,6-dialkyl substituted phenol and this bisetherification reaction is against scientific fact as explained hereabove.
This invention has been made under such circumstances.
The object of this invention is to provide a process for production of alkoxyalkyl group substituted phenols in high yields where the objective product and catalyst can be easily separated.